1. Technical Field
The present disclosure relates to a cable assembly, in particular, to an adjustable matched cable assembly and a signal transmission system thereof.
2. Description of Related Art
In the environment which the information transmission develops rapidly, the communication technology is improved day by day accompanying with the requirements of users. However, it needs high transmission quality for the radio frequency (RF) or microwave signal transmission.
In general, since the microwave system almost uses the differential signal for transmission, the two cables for signal transmission need high accuracy of phase matching. In other words, the phase error between two signals transmitted by the two cables must be within the range. Therefore, each cable in the cable assembly must have a specific electrical length according to the manufacture specification. In the application of the cable assembly requiring phase matching, the ideal situation is that the each cable in the cable assembly has the same or similar electrical length to each other.
Please refer to FIG. 1. FIG. 1 is a stereoscopic diagram of the traditional cable assembly. The traditional cable assembly 9 comprises a first cable 91 and a second cable 92. The first cable 91 has two fixed (or immovable) contacts 9101, 9102 at both ends thereof, and the second cable 92 has two fixed contacts 9201, 9202 at both ends thereof in the similar manner. Since the first cable 91 and a second cable 92 shall have the equal or approximate electrical lengths to each other, the signals respectively transmitted by the first cable 91 and the second cable 92 have the small phase error between each other, and the correct differential signal is therefore formed by the signals respectively transmitted by the first cable 91 and the second cable 92.
Although the electrical length relates with the physic length in the practical application, the electrical length error of the between the cables having the same physic length still exists. Therefore, during the process for manufacturing the cable assembly, a large number of cables with the approximate physic lengths are firstly manufactured. Then, during the process for selecting the cables, two cables of the cables are selected to be tested repeatedly, and two cables which have the electrical length error therebetween within the specific range are selected out as the cable assembly according to the test results. By using the abovementioned method, the cost for manufacturing numerous cables is increasing while the microwave (or RF) device (or system) may require the cables with the long physic length. In a word, the conventional method for manufacturing the matched cable assembly consumes the massive cost and the time of selection and testing.